Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -92,7 +92,7 @@ When making a pull request, please ensure it [the PR] follows these best practis
 - Targets `develop` (unless it explicitly depends upon another feature, then depend on that branch and comment to that effect in the PR body).
 - Is updated via rebase mechanisms when `develop` changes, rather than merge commits (reduces noise).
 - Is [signed off](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#sign-off). Matrix.org projects require that the
-   sign off process has been followed in it's entirety.
+   sign off process has been followed in its entirety.
 - Has a [changelog entry](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#changelog) in `changelog.d`.
   A changelog filename should be `${GithubPRNumber}.{bugfix|misc|feature|doc|removal}`.
   The change should include information that is useful to the user rather than the developer.
@@ -131,4 +131,4 @@ When reviewing a PR, a maintainer will:
 This guide aims to cover all bases to get new contributors started, but it won't be able to satisfy every question. If
 you have any other questions, please seek us out in any of the project rooms and we will be happy to assist! Other than that,
 thanks for taking the time to read this and improving our projects for
-the benefit of all 😄
+the benefit of all 😄